Positive effect of winter dormancy on cold-blooded cognition

11.01.2017: Unlike mammals, amphibians who rest-up during the winter do not forget the memories they made beforehand – this is the surprising discovery of new scientific research published. A new study, by researchers from the Messerli Research Institute of Vetmeduni Vienna and University Vienna and University of Lincoln, reveals that the processes involved in winter dormancy may have a fundamentally different impact on memory in amphibians and mammals. The study was published in the journal Scientific Reports.

Researchers from the Messerli Research Institute of Vetmeduni Vienna and University Vienna and University of Lincoln discovered that brumation – the period of winter dormancy that is observed in cold-blooded animals, similar to the process of hibernation in mammals – does not seem to adversely affect the memory of salamanders.

This key finding differs dramatically from previous studies of mammals, which show that hibernation often causes animals to forget some of the memories they formed prior to their period of inactivity.

Effect of hibernation on cognition unknown for coldblooded

Ludwig Huber, head of the Unit of Comparative Cognition of the Messerli Research Institute of Vetmeduni Vienna and the University of Vienna and Anna Wilkinson, University of Lincoln, explained: “Long-term torpor is an adaptive strategy that allows animals to survive harsh winter conditions. However, the impact that this has on cognitive function is poorly understood. We know that in mammals, hibernation causes reduced synaptic activity and can cause them to lose some of the memories they formed prior to hibernation, but the effect of brumation on memory has been unexplored, until now.

Salamanders remember after torpor, mammals do not after hibernation

The researchers trained twelve salamanders to navigate a T-maze and remember the path they needed to take to reach a reward. Half of the animals were then placed into brumation, while the other half continued under normal keeping conditions. A post-brumation memory retention test revealed that animals from both conditions recalled how to navigate the maze.

“We demonstrated that each of the animals solved the task using memory, rather than sensory cues such as smell of the reward,” Huber said, The scientists therefore confident that the period of brumation did not impact on their ability to remember. “For these animals, memory retention is essential for survival as it allows them to recall important information about the environment, such as the location of food and the presence of predators”, explains Wilkinson.

Type of dormancy obviously directs cognition

The researchers suggest that the differences in retention observed between mammals and amphibians could be caused by their different learning and memory processes, or the nature of their torpor. Mammals regularly rouse from their hibernation and enter intervals of sleep, whereas cold-blooded animals are dependent on the temperature of their surroundings during brumation and are therefore forced to stay torpid until temperatures rise.